On the one hand, this plug and the cooperation of the plug with the housing are required to have great tightness. The great tightness effectively and permanently suppresses the penetration of harmful liquids and gases, for example those that trigger corrosion, into the interior of the exhaust gas sensor. To achieve the tightness, the plug is in particular required to have sufficient elasticity. Due to the high exhaust gas temperatures to which the exhaust gas sensor is exposed, on the other hand only materials which have a corresponding high temperature resistance may be used for the stopper.
German patent document DE 10 2005 020 793 A1 refers to providing a plug made of polytetrafluoroethylene, also known as PTFE, for closing the housing of an exhaust gas sensor. Force-fit sealing between the housing and a cable lead-through of the exhaust gas sensor with the aid of a tube made of fluorine-containing plastic is provided.